The Trademark Clearinghouse is investigating the causes and impact of an outage that is believed to have hit its primary database for 10 hours last Friday.

Some in the intellectual property community are concerned that the downtime may have allowed people to register domain names without receiving Trademark Claims notices.

The downtime was confirmed as unscheduled by the TMCH on a mailing list, but requests for more information sent its way today were deflected to ICANN.

An ICANN spokesperson said that the outage is being analyzed right now, which will take a couple of days.

The problem affected the IBM-administered Trademark Database, which registrars query to determine whether they need to serve up a Claims notice when a customer tries to register a domain that matches a trademark.

I gather that registries are supposed to reject registration attempts if they cannot get a definitive answer from the TMDB, but some are concerned that that may not have been the case during the downtime.

Over 145,000 Claims notices have been sent to trademark owners since the TMCH came online over a year ago.

(UPDATE: This story was edited May 21 to clarify that it is the TMCH conducting the investigation, rather than ICANN.)

The popular “emoji” smiley faces are banned as gTLD domain names for technical reasons, according to ICANN.

Emojis are a form of emoticon that originated on Japanese mobile networks but are now used by 12-year-old girls worldwide due to their support on Android and iPhone operating systems.

It emerged last week that Coca-Cola has registered a bunch of smiley-face domain names under .ws, the Samoan ccTLD, for use in an billboard advertising campaign in Puerto Rico.

.ws was selected because it’s one of only a few TLDs that allow emojis to be registered. Coke is spinning its choice of TLD as an abbreviation for “We Smile”.

This got me thinking: would emojis be something new gTLD registries could start to offer in order to differentiate themselves?

Coke’s emoji domains, it turns out, are just a form of internationalized domain name, like Chinese or Arabic or Greek.

Emoji symbols are in the Unicode standard and could therefore be converted to the ASCII-based, DNS-compatible Punycode under the hood in web browsers and other software.

One of Coke’s (smiley-face).ws domain names is represented as xn--h28h.ws in the DNS.

Unfortunately for gTLD registries, ICANN told DI last night that emojis are not permitted in gTLDs.

“Emoticons cannot be used as IDNs as these code points are DISALLOWED under IDNA2008 protocol,” ICANN said in a statement.

IDNA2008 is the latest version of the IETF standard used to define what Unicode characters can and cannot appear in IDNs.

RFC 5892 specifies what can be included in an IDNA2008 domain name, eliminating thousands of letters and symbols that were permissible under the old IDNA2003 standard.

These characters were ostensibly banned due to the possibility of IDN homograph attacks — when bad guys set up spoof web sites on IDNs that look almost indistinguishable from a domain used by, for example, a bank or e-commerce site.

But Unicode, citing Google data, reckons symbols could only ever be responsible for 0.000016% of such attacks. Most homograph attacks are much simpler, relying on for example the visual similarity of I and l.

Regardless, because IDNA2008 only allows Unicode characters that are actually used in spoken human languages, and because gTLD registries are contractually obliged to adhere to the IDNA2008 technical standards, emojis are not permitted in gTLDs.

All new gTLDs have to provide ICANN with a list of the Unicode code points they plan to support as IDNs when they undergo pre-delegation testing. Asking to support characters incompatible with IDNA2008 would result in a failed test, ICANN tells us.

ICANN does not regulate ccTLDs, of course, so the .ws registry is free to offer whatever domains it wants.

However, ICANN said that emoji domains are only currently supported by software that has not implemented the newer IDN protocol:

Emoticon domains only work in software that has not implemented the latest IDNA standard. Only the older, deprecated version of the IDNA standard allowed emoticons, more or less by accident. Over time, these domains will increasingly not work correctly as software vendors update their implementations.

So Coke, while winning brownie points for novelty, may have registered a bunch of damp squibs.

ICANN also told us that, regardless of what the technical standards say, you’d never be able to apply for an emoticon as a gTLD due to the “letters only” principle, which already bans numbers in top-level strings.